Magnetic MnFe2O4 activated peroxymonosulfate processes for degradation of bisphenol A: Performance, mechanism and application feasibility

Magnetic ferrites were used as heterogeneous peroxymonosulfate (PMS) activators for bisphenol A (BPA) degradation, in which activation performance, mechanism and application feasibility were investigated in depth. The results demonstrated that BPA depletion in ferrites activated PMS processes could be described by pseudo-first-order kinetic model and the BPA degradation was in the sequence of CoFe2O4 > MnFe2O4 > CuFe2O4 > Fe3O4. Comprehensive consideration of activation performance, operating cost and toxicity risk, MnFe2O4 might be the most ideal PMS activator. MnFe2O4/PMS process could efficiently work in wide pH range of 4.0-10.0 and acidic pH was more favorable for the oxidation. The introduction of natural organic matter, sulfate, bicarbonate and low concentration of chloride retarded BPA removal. Contrastingly, the presence of high level of chloride greatly stimulated the degradation. A reasonable mechanism for PMS activation by MnFe2O4 was evidenced by free radical identification and XPS measurements, illustrating that the cycles of Mn(II)-Mn(III)-Mn(II) and Fe(III)-Fe(II)-Fe(III) were involved during the oxidation and sulfate and hydroxyl radicals were both responsible for BPA degradation. MnFe2O4 showed excellent reusability and long-term stability, which was testified by the detailed characterizations of fresh and spent catalysts. MnFe2O4 /PMS process not only achieved efficient degradation of different emerging organic pollutants in ultrapure water, but gained high-efficient depletion of low concentration of BPA in surface waters. More importantly, potential risk derived from BPA degradation could be effectively controlled by MnFe2O4/PMS process.